In recent years, telephone companies have increased the use of optical fibers throughout the telephone system. Optical fibers provide a significant increase in communication bandwidth per cross-sectional area of the cables. Further, optical fibers are much better suited for high speed digital communication than traditional copper wires.
Because of the greater bandwidth efficiency, optical fiber cables have been used to replace the loop "feeder" (high cross-section) cables in the telephone networks. Increasingly, however, the telephone companies are interested in replacing the loop "distribution" cables (end cables between the feeder cables and the customers) in order to provide additional higher bandwidth services than are offered currently. For example, video could be transmitted over optical fibers to a customer's home or place of business.
Unlike the present copper distribution cables, an optical fiber cable cannot conduct electricity for power of the optical network units coupling the distribution cable to the customer. Thus, either a copper wire must be cabled in parallel with the optic fiber, or a local power supply (typically derived from the power company) must supply the power.
In either instance, loss of power to the optical network unit ("ONU") that terminates the optical fibers at or near the customer's premises is an occurrence which will result in loss of service. The telephone company preferably may effectively diagnose the problem associated with a loss of service from a remote maintenance center. For effective diagnostics, it is important that the telephone company be able to distinguish a failure of the fiber connected to the optical network unit, failure of the optical network unit itself, and the loss of power in the optical network unit. Moreover, it is important for the telephone company to identify whether a problem originated in the telephone company's own equipment or in the customer's equipment, so that the telephone company may take appropriate actions prior to the dispatching of repair personnel, such as notifying the customer in advance about fees if telephone company repair personnel are dispatched to repair customer-owned equipment.
Thus, a need has arisen for a method and apparatus for monitoring power loss in a telecommunications system, such that the loss of power indication is differentiated from an optical cable or ONU electronic failure in order to facilitate rapid diagnosis and service restoral, and such that a problem originating in the telephone company's own equipment may be differentiated from a problem originating in the customer's equipment.